1. The Field of the Invention
This invention relates to improved dental kits and procedures for sealing noncarious or slightly carious pits and fissures in teeth to aid in the prevention of dental caries. More specifically, the invention relates to an improved dental pit and fissure sealant kit consisting of an etching material, a drying/priming agent, and a resinous sealant which is applied over naturally occurring noncarious dental pits and fissures or after carious lesion removal to protect a tooth from cariogenic attack.
2. The Relevant Technology
With the appearance of resins and resinous composites in the field of dentistry, a variety of uses and bonding techniques have been developed besides the mere filling of cavities. In some cases, composites, the name for highly filled resins, can take the place of traditional silver-mercury amalgam, particularly when the hardness and durability of amalgam is not required. In addition, lesser filled resins are ideal for many cosmetic alterations of the teeth, such as applying a layer of white resinous material for concealing unattractive stains, or otherwise brightening one's smile.
Unfilled and low filled resins have been found to be useful in filling noncarious pits and fissures found naturally in teeth, usually molars. While often not the product of tooth decay but natural tooth development and formation, such pits and fissures are usually more difficult to clean and are ideal locations for cariogenic agents to lodge, eventually resulting in the formation of caries (or cavities).
The depth and width of naturally occurring pits and fissures varies greatly among the population. Generally, the deeper the fissure, the greater the chance the tooth will eventually suffer decay. As a measure to prevent tooth decay and cavity formation, dentists have more recently begun to partially fill the deepest portions of these pits and fissures with resinous materials.
Before placing an appropriate resinous material within the pit or fissure being treated, the enamel is normally prepared in order to allow reliable adhesion of the polymeric resin material to the enamel. By methods known in the art, the enamel is physically scraped or buffed with a rotary burr in order to remove all foreign materials such as dental plaque or tartar.
The enamel is then chemically etched with an aqueous acid such as phosphoric or citric acid to further prepare the tooth surface to be bonded. Etching selectively removes various components of the enamel, thereby creating microscopic irregularities and undercuts. The surface is then dried with air and the pits and fissures are sealed with the resinous filling material.
However, air drying alone is not capable of completely drying the enamel and the area within the pits and fissures. Because teeth and enamel are located in a 100% humid environment, a thin film of water can adhere to the enamel with tenacity. Sources of moisture include the saliva present in the patient's mouth, the aqueous acid etch, and even ambient water vapor present in the mouth. Due to the small width, combined with the relatively large depth, of typical pits and fissures, it is especially difficult for air drying alone to effectively remove moisture from within the pits and fissures. In addition, most compressed dental air sources unfortunately contain moisture.
The failure to completely dry the enamel surface prior to applying the pit and fissure sealant decreases the ability of the sealant to adequately bond to the enamel, which increases the likelihood of subsequent microleakage of the bonded filling. Hence, the success of the sealing process often correlates to the success of completely drying the enamel surface.
Resinous materials tend to shrink upon curing causing them to pull away from the tooth surface, especially if a strong bond has not been achieved between the resin and the enamel surface. Such bonding is more difficult if the enamel has not been adequately dried of excess moisture.
When there is microleakage of moisture into the interface between the enamel surface and the sealant, the anticarious properties of the sealant are greatly diminished. In fact, microleakage probably increases the possibility of developing caries in the pit or fissure that was treated because of the difficulty of removing a cariogenic agent (bacteria or their byproducts) that has crept into the interface between the tooth and sealant.
Ordinary cleaning regimens such as brushing or gargling are inadequate in cleaning, flushing out or otherwise removing cariogenic agents that might creep into the interface between the sealant and enamel. Thus, microleakage tends to undermine the reason for sealing the pit or fissure in the first place.
Improvements in the bond between resin and enamel have been achieved through the use of drying agents, usually water miscible organic solvents such as acetone or ethyl alcohol. While using such solvents has the advantage over simply drying the enamel by air, they still do not result in completely reliable bonding between resin and enamel. This is mainly due to the enormous difference in the relative polarities between enamel and most resins, enamel being extremely hydrophilic, while resins are largely hydrophobic. Thus, resins and enamel have a natural tendency to repel each other.
Thus, even if the excess water has been removed from the tooth, the problem remains that the largely hydrophobic resins found in pit and fissure sealants cannot effectively "wet" or make sufficiently intimate, interactive contact with the very hydrophilic enamel surface. This is yet another impediment of prior art sealing methods in attaining reliable adhesion between the resinous sealant and tooth enamel.
In view of the foregoing, it would be an advancement in the dental art to provide dental compositions and procedures for applying resinous sealants to dental pits and fissures which would result in a more reliable adhesion of the sealant and the elimination of microleakage. It will be appreciated that it would also be a significant improvement over the prior art to provide dental compositions and procedures which would substantially eliminate the separation of the applied sealant from the enamel surface due to the inability to effectively remove the thin film of water from the tooth surface. Therefore, what is needed are compounds and procedures for more effectively removing water from tooth enamel surfaces prior to the application of resinous sealing materials.
It would be a further advancement in the dental art to provide compositions and procedures which effectively "wet" the enamel surface and reduce the hydrophilic nature of the surface so that the hydrophobic sealing material can make more intimate contact with the enamel. Such compositions and procedures would result in greater bond strengths between the enamel and sealing material and significantly reduce or eliminate the microleakage caused by shrinkage of the polymerizing composite materials in conjunction with the lack of adequate initial wetting of the enamel surface by the applied resinous sealing composite.
Such compositions and procedures for achieving these results are set forth and claimed herein.